Direct and inverse Hall effects: A consequence of both Ampere's law and electron spin?
DIPC Seminars
 Speaker

Antonio Hernando, Universidad Complutense Madrid, Spain
 When

2019/12/05
13:00  Place
 Donostia International Physics Center
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We analyse the contribution of the inhomogeneous magnetic field induced by an
electrical current to the spin Hall effect in metals. In fact the field
produced by the current cannot act on the current itself but the field
produced by the relative motion of the lattice does it. The Zeeman coupling
between the field, seen at the reference frame in which the carriers are at
rest, and the electron spin leads to a force that accumulates spin at the
edges. It is shown that this spin Hall effect can be expressed as two opposite
ordinary Hall effect in which the applied fields are the saturation
magnetization of both subbands. In other words the force exerted by the
lattice current on the electron, ( Â±(Âµâˆ‡)B where B is the field seen by the
electrons and Âµ the spin magnetic moment) is equal but opposite to that
exerted by the electrons on the lattice current ( Â± jÂµ_0 M, where M is the
saturation magnetiztion of Â± spin subbands. )
The inverse spin Hall effect is also explained under the same basis. Finally,
by considering the effect of the possible spontaneous magnetization of the
lattice, a new perspective for understanding the anomalous Hall effect is
open.
It is concluded that , the Lorentz force, the Zeeman energy and the spin of
the electron are ingredients sufficient to account for the first order
characteristics of the spin Hall effect.
Within our explanation, that does not interact with other possible
contributions, we remark the following characteristics
a) The field produced by the lattice current on the carrier system defines a
spin direction
b) Not explicit dependence of the effect strength on the atomic spinorbit
coupling of the metal is envisaged at first order
c) The huge dispersion of experimental results can be understood through the
geometrical dependence of the magnetic field strength and distribution
d) The effect of the macroscopic field is naturally introduced, otherwise a
non realistic assumption as that implict in Hirsch discussion: â€œ the number
of impurities is equal to the number of lattice atoms and all of them are
identicalâ€ has to be established a priori
e) The order of magnitude of both spin and charge imbalances inferred from our
considerations is that found in the literature
Host: Ricardo DÃez MuiÃ±o